Strong Light Intensifications Yielded by Arbitrary Defects: Fresnel Diffraction Theory Applied to a Set of Opaque Disks

Abstract

Two centuries ago, Fresnel, Poisson, and Arago showed how the wave nature of light induces a bright spot behind an opaque disk. We develop an analytical model based on the Fresnel diffraction theory to show how small perturbations such as digs or scratches can yield intense light enhancements on the downstream axis. The impact of defects with complex morphology on light diffraction is shown to be accurately modeled by the Fresnel theory applied to a set of opaque disks characterized by phase shift and transmittance. This model can be used either to define the geometry of the defects that optimizes the light enhancement or to improve the defect specification on the surface of the optical components. We explain why partial information of the defect morphology can suffice to specify a safety distance beyond which light intensifications are not dangerous. The validity of this analytical approach is studied by measuring the intensifications created by three different microdefects.

Application of light diffraction theory to qualify the downstream light field modulation property of mitigated KDP crystals

“…In addition to the improved laser damage resistance, Matthews et al [18] found that the mitigated contours may cause the laser damage on the downstream optics element due to the light field modulation. Based on Fresnel diffraction theory, Tournemenne et al [19] developed an analytical model to show how small perturbations, such as digs or scratches, can yield intense light enhancements on the downstream axis. Zheng et al [20] also discovered that a special configuration of the laser damaged coating causes wave-front modulation, which affects the downstream light field propagation.…”